1. Field of the Invention
The present invention relates to semiconductor devices and fabrication methods thereof, and more particularly to wirings for semiconductor devices composed of multi-layer type (laminated films) of an Al-Si-Cu alloy film and a refractory metal (having high melting point) silicide film and fabrication methods thereof.
2. Description of the Prior Art
Aluminum-based alloy films have been used widely for a long time as wiring materials of semiconductor devices. In the old days, aluminum films alone had been used. As the depth of diffused layers became small, Al-Si alloy films began to be employed in order to deal with the so-called alloy spike phenomenon. With the patterns of the semiconductor devices becoming finer, the current density for wirings increased first, and the electromigration became an important problem in reliability. This phenomenon is accompanied with Si precipitation, micro-void growth and the like which could not be handled by means of the Al-Si alloy films. This is the reason why Al-Si-Cu alloy films became to be introduced. Use of these alloy films cause CuAl.sub.2 to be precipitated at the grain boundaries, and CuAl.sub.2 thus formed blocks the mass transport of Al by the current. In addition, as the wiring width approaches the grain size due to the patterns of the semiconductor devices becoming finer, the stressmigration phenomenon was made visible. Under the circumstances, that the Al-Si-Cu alloy films are powerless against the stressmigration failure, laminated films consisting of an Al-Si-Cu alloy film and an refractory metal silicide film began to be introduced.
This laminated film is undoubtedly effective for stressmigration failure. However, this laminated film is inferior to the Al-Si-Cu alloy in electromigration resistance.
This fact was reported by an article titled "COMPARISON OF ELECTROMIGRATION PHENOMENON BETWEEN ALUMINUM INTERCONNECTION OF VARIOUS MULTILAYERED MATERIALS" by T. Fujii et al. in the digest of papers for the 1989 VMIC Conference sponsored by IEEE, pp. 477-483. This report gives an analysis which focuses attention on the behavior of Si.